The present invention relates to an optical image processor, and more particularly, to an improvement of an optical image processor applicable to analog parallel processing and display of a moving or still picture, etc.
FIGS. 1 and 2 show conventional optical image processors 1a and 1b respectively, which were made known in the lecture of applied physics society in fall, 1989.
The optical image processor la shown in FIG. 1 will be explained first. In the figure, a photoconductive member 14 of bismuth silicon oxide (BSO) and dielectric mirror 12 are laminated to a liquid crystal complex member 10 of polymer and nematic liquid crystal. Those are sandwiched between transparent electrodes 16 and 18 of indium tin oxide (ITO). Further, a glass substrate 20 is laminated to the transparent electrode 18. A power supply 21 for driving the optical image processor la is connected across the transparent electrodes 16 and 18.
In the case of image writing, a beam of light (a writing light) such as an Ar laser beam is radiated to the photoconductive member 14 via the transparent electrode 16 as depicted by an arrow Fl. An optical image carried by the laser beam is stored in the photoconductive member 14 as a charge image.
On the other hand, in the case of image reading, a beam of light (a reading light) such as He-Ne laser beam is radiated to the liquid crystal complex member 10 via the glass substrate 20 and transparent electrode 18. The liquid crystal complex member 10 is applied with an electric field due to the charge image in the photoconductive member 14. The reading light is thus modulated according to the charge image. The modulated reading light is then reflected at the dielectric mirror 12 and emitted out from the optical image processor la as depicted by an arrow F3.
Next, the optical image processor 1b shown in FIG. 2 will be explained. In FIG. 2, a liquid crystal cell 22 is laminated with a photoconductive member 24 of hydrogenated amorphous silicon (a-Si:H) of i-type. Those are sandwiched between transparent electrodes 26 and 28 of ITO. Further, glass substrates 30 and 32 are laminated to the transparent electrodes 26 and 28, respectively. A power supply 34 for driving the optical image processor 1b is connected across the transparent electrodes 26 and 28. Writing and reading operation of the optical image processor 1b is the same as those explained with reference to FIG. 1.
However, in the above-mentioned optical image processors 1a and 1b, material of the photoconductive member for forming the charge image and dielectric mirror have relatively low resistivity, that is, .rho.&lt;10.sub.10 .OMEGA..cm. Therefore, electric charges of the charge image are transferred to the portion of the photoconductive member to which a writing light of weak optical intensity is radiated from the portion thereof to which a writing light of strong optical intensity is radiated. This results in a reduction in the contrast and resolution of a reproduced optical image.
Particularly, the photoconductive member 14 in FIG. 1 is composed of BSO so that a blue writing light only can be used for the image writing. On the other hand, the photoconductive member 24 in FIG. 2 is composed of a - Si: H so that the writing light is not limited to the blue writing light. However, a-Si:H is less sensitive to light in the region under 600 nm of wavelength and optical transmittance of a-Si:H exhibits almost 0% in that region as shown in FIG. 3. Therefore, a charge image is formed only in the vicinity of the surface of the photoconductive member 24. Accordingly, writing of an optical image to the optical image processor 1b in that region is very difficult.